Communications networks, which utilise an Internet Protocol (IP), provide a facility for communications nodes, such as personal computers, mobile devices and servers to communicate information during communications sessions. According to the Internet Protocol used, each communications node is provided with an IP address, which uniquely identifies that node within the IP network. These IP addresses may be either permanently assigned to a communications node, or assigned at a time at which a node affiliates itself with the network. More recently, access to IP networks has been possible using mobile nodes such as mobile phones and portable computers. For example, a mobile node may access an IP network via some form of wireless connection, for instance by a radio communications network or an infra-red link. As such an IP address may be assigned to a communications node on a temporary basis, which may change during a communications session. Accordingly, the communications session may be affected by a change of the IP address of the mobile node, resulting from, for example, a change of affiliation from one network to another during a communications session.